1. Field of the Invention
The present invention relates generally to medical examining instruments and in particular to a calibrated glove for taking obstetrical measurements.
2. Description of the Prior Art
In medical practice, and particularly obstetrics, internal measurements are often necessary for purposes of evaluating the patient's condition. In obstetrics, certain internal measurements are important prior to the onset of labor to anticipate potential delivery problems and other measurements are important during labor to monitor the patient's and her baby's progress.
Specifically, the conjugate diameter of the pelvic inlet, as measured from the promontory of the sacrum to the symphysis pubis is important to determine if the pelvic inlet is of sufficient size to permit normal delivery. In practice, a measurement comprising the diagonal conjugate is generally taken from the sacral promontory to the lower margin of the symphysis pubis. The true obstetric conjugate can then be determined by subtracting 1.5 to 2 centimeters from the diagonal conjugate. "Williams Obstetrics," by Jack A. Pritchard, Paul C. MacDonald and Norman F. Gant, 17th Ed. (1985), published by Appleton-Century-Krafts, Inc., New York, N.Y.
In a common prior art method of measuring the conjugate diameter, the examiner inserts his or her index and middle fingers into the patient's vagina and engages the sacral promontory with the tip of the middle finger. The index finger of the other hand is then placed against the symphysis pubis and the base of the inserted index finger and the inserted hand is withdrawn so that the noted distance can be measured. The Biscow U.S. Pat. No. 2,394,140 discloses a glove with scales along the index finger for measuring the conjugate diameter. Also, the Cuadros U.S. Pat. No. 3,643,651 discloses a scale with a stirrup for placing over the examiner's middle finger and a calibrated strip extending therefrom.
Another important pre-labor obstetric measurement is the bisischial diameter, which is defined as the distance between the ischial spines at midpelvis. The fetal head must be small enough to pass between the ischial spines. Prior art devices for determining the bisischial diameter include that shown in the Horton U.S. Pat. No. 3,097,637 which includes an elongated stem with a short length of chain attached to one end and terminating in a ring. The ring is placed over a finger of the examiner and engaged against one of the ischial spines with the end of the stem engaging the other ischial spine. If the chain can be fully extended the bisischial diameter is considered adequate for delivery of a normal-sized fetus.
The aforementioned obstetric measurements are significant for determining if a disproportion exists between the size of the baby's head and the mother's pelvis prior to the onset of labor. By prediagnosing such a condition, the physician can determine if a delivery by cesarean section is indicated on the basis of pelvic contracture.
Another important obstetrical internal dimension is the diameter of the patient's cervix. Prior to the onset of labor a normal cervical canal has a diameter of zero to three centimeters. During labor, dilatation to approximately ten centimeters, a condition often referred to as "complete" or "fully dilated", must occur to pass the head of the average fetus through the cervix. Accordingly, the patient's progress through the first stage of labor can be determined by monitoring the cervical diameter. The patient's rate of change of cervical dilatation is significant to the physician, and can be determined from accurate and periodic measurements of the cervical diameter taken between the lower lips or rims of the cervix at the level of the internal os. The cervical diameter may also be important in detecting the premature onset of labor and in monitoring the effectiveness of tocolytic drugs in slowing or halting dilatation and the progress of labor.
A common method of roughly approximating the patient's cervical diameter involves the insertion of two or more fingers into the vagina and thence digitally contacting the lips or rims of the cervix. Based upon the relative position of his or her fingers, the examiner estimates the patient's cervical dilatation. However, digitally estimating the cervical diameter in this subjective manner tends to yield relatively inaccurate results which can vary widely between different examiners. For example, the size of the examiner's fingers and his or her experience might influence the estimation of the patient's dilatation. There is also a human tendency to overstate the true amount of dilatation to reassure the laboring patient that delivery will come soon and that her suffering will end. Furthermore, during labor a patient may be checked by several different examiners, whose methods and results may not be consistent.
The lack of accurate information on the cervical dilatation of patients is, at best, a source of frustration to obstetricians who, because of very tight schedules, are often not summoned until the woman is thought to be complete. Obviously if the patient is misdiagnosed as being complete, the obstetrician may arrive well before his or her presence is required. On the other hand, understating the patient's dilatation can have the opposite effect. Most importantly, accurate detection of a patient's lack of progress in labor at an early stage serves to alert the physician that further evaluation and alternative therapy may be indicated.
Various devices are known for measuring cervical dilatation. For example, the Von Micsky U.S. Pat. No. 2,924,220 and the Krementsov U.S. Pat. No. 4,207,902 U.S. patents show devices with arms for engaging the lips of the cervix and providing a measurement reading. However, such devices tend to be impractical, cumbersome, painful and relatively expensive. Furthermore, they require sterilization between each insertion to avoid the introduction of bacteria into the vagina and uterus.
The Farr et al. U.S. Pat. No. 4,245,656 discloses obstetric gloves with a measuring string coiled within one finger and extending to an adjacent finger. However, the measuring string of this device cannot be reset with the examiner's fingers inserted in the patient. Also, the fingers must be withdrawn to determine the measurement.
Another disadvantage with cervical measurements taken digitally relates to the possibility of introducing bacteria into the patient. Although standard procedure is for the examiner to wear a sterilized glove, cervical measurements taken digitally may be repeated often during labor, in part because of the relative uncertainties in the measurements. The frequency of examination not only increases the risk of infection but also adds to the discomfort of the patient.
Fetal progress during labor is monitored by comparing the position of the fetal head with respect to the ischial spines of the mother. The fetal position is designated by stations indicating the distance in centimeters between the lowermost portion of the fetal head and the bisischial diameter. Negative stations indicate the fetal head being located above the bisischial diameter and positive stations indicate a position below. When the fetal head reaches station plus five it is usually visible and is said to be "crowning". As with other obstetric measurements, the baby's descent station is often estimated subjectively by digital examination with resulting inaccuracies.
Heretofore there has not been available an examining glove for taking the aforementioned measurements with the advantages and features of the present invention.